Definitions

Question 1

Periodicity

Answer 1

Quality or character of being repeated at intervals

Question 2

Valency

Answer 2

The number of electrons in the outer shell of an atom which are able to form bonds with other atoms

Question 3

Molar mass

Answer 3

The mass in grams of one mole of that substance

Question 4

Halide

Answer 4

Binary compound of a halogen with another element or group of elements

Question 5

Oxide

Answer 5

An ion of oxygen

Question 6

Molecular formula

Answer 6

Concise way of expressing information about the atoms that make up a particular covalent molecular compound. Gives the exact number of each type of atom in molecule

Question 7

Empirical formula

Answer 7

Shows the simplest ratio of atoms in the compound

Question 8

Physical change

Answer 8

A change that does not alter the chemical nature of the substance, no new chemical substances are formed

Question 9

Chemical change

Answer 9

A change in which the chemical nature of the substances involved changes, new chemical substances are formed

Question 10

Law of constant proportions

Answer 10

Sometimes called Proust’s law or the law of definite composition, states that a chemical compound contains exactly the same proportion of elements by mass

Question 11

Law of conservation of mass

Answer 11

The total mass of a substance taking part in a chemical reaction is conserved during the reaction

Question 12

Dissolving/ dissolution

Answer 12

Solid ionic crystals breaking up into ions in H2O

Question 13

Dissociation

Answer 13

Process in which ionic compounds separate into smaller ions

Question 14

Hydration

Answer 14

Where ions become surrounded with water in solution (no IMF- only the polarity of the water molecule and the charge of the ions)

Question 15

Electrolytes

Answer 15

A substance that contains free ions and behaves as an electrically conductive medium

Question 16

Precipitate

Answer 16

The solid that forms in solution during a chemical reaction

Question 17

Precipitate reactions

Answer 17

Chemical reactions where solids form when two solutions of soluble salts react.

Question 18

Ion exchange reaction

Answer 18

Reaction where the positive ion exchange their respective negative ions due to a driving force

Question 19

Acid base reaction

Answer 19

Reaction in which an acid reacts with a base to form a salt and water

Question 20

Mole

Answer 20

SI unit for amount of substance

Question 21

Avogadro’s number

Answer 21

The number of particles in a mole of substance

Question 22

Molar volume of gases

Answer 22

One mole of gas occupies 22,4 dm3 at standard temperature and pressure

Question 23

Concentration

Answer 23

The amount of solute per unit volume of solution

Question 24

Stoichiometry

Answer 24

The study of the relationship between the relative quantities of substances taking part in a reaction or forming a compound, typically a ratio of whole integers

Question 25

Hydrate

Answer 25

A compound, typically a crystalline one, in which water molecules are chemically bound to another compound or element

Question 26

Water of crystallisation

Answer 26

Water molecules forming an essential part of the crystal structure of some compounds

Question 27

Percentage composition

Answer 27

The percentage by mass of each element in the compound

Question 28

Decomposition reaction

Answer 28

A type of chemical reaction in which a single compound breaks down into two or more elements or new compounds

Question 29

Synthesis reaction

Answer 29

A type of chemical reaction in which two or more simple substances combine to form a complete product

Question 30

Exothermic reaction

Answer 30

Reactions which transform chemical potential energy into thermal energy

Question 31

Endothermic

Answer 31

Reactions which transform thermal energy into chemical potential energy

Question 32

Yield

Answer 32

The measure of the extent of the reaction, generally measured by comparing the amount of product against the amount of product that’s possible